We present the influence of both the solid-liquid interfacial force (surface wettability) and liquid-liquid interfacial force (added surfactants) on water-oil two-phase flow in microfluidic devices. Experimental results show that, in contrast to macroscale experiments, the surface wettability crucially determines the emulsion type created in the microchannels: O/W in hydrophilic channel and W/O in hydrophobic channel. Surfactants, however, determines the flow pattern, changing from droplet-based to stratified flow by decreasing wo.